New maps do not follow normal rules of expansion if another map has been made in the same area. The general rule is that when expanded, map will add more terrain away from the player. However, if there is another map in the world that has been expanded in a certain direction, future maps made and expanded in the same area will always mimic the existing map, regardless of where the player is standing. The linked video does a better job of explaining it

https://www.youtube.com/watch?v=5JogJ0ugBVI